Liquid crystal display device and fabricating method thereof

ABSTRACT

A liquid crystal display device that reduces manufacturing cost, contributes to a thin profile, and generates uniform brightness, and a fabricating method thereof are disclosed. 
     In the liquid crystal display device, a liquid crystal display panel is prepared. A backlight includes a plurality of lamps, a diffusion plate which is located on the lamps, and an intermediate diffusion medium located between the lamps and the diffusion plate to diffuse light from the lamps, and irradiates light to the liquid crystal display panel. 
     Furthermore, in the method of fabricating the liquid crystal display device, a diffusion material is molded using a mold to form an intermediate diffusion medium that includes a plurality of ribs connected to an external band of square type and both sides of the external band of square type, respectively. The intermediate diffusion medium is located between lamps and a diffusion plate.

This application claims the benefit of Korean Patent Application No.P2006-0119794, filed in Korea on Nov. 30, 2006, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device and afabricating method thereof, and more particularly to a liquid crystaldisplay device that may reduce manufacturing cost, contribute to a thinprofile, and generate a uniform brightness, and a fabricating methodthereof.

2. Discussion of the Related Art

Liquid crystal display devices are widely used due to their being lightweight, having a thin profile and low power consumption, for example. Asa result, the liquid crystal display device is used in office automationequipment and audio/video equipment, for example. The liquid crystaldisplay device controls the amount of light in accordance with a signalapplied to a plurality of control switches that are arranged in amatrix, thereby displaying a desired picture on a screen.

As such, the liquid crystal display device is not a self luminousdisplay device, thus it requires a separate light source such as abacklight.

Backlights may be largely classified as either direct type or edge typein accordance with the location of a light source. The edge typebacklight has a light source installed at the edge of one side of aliquid crystal display device, and the edge type backlight irradiateslight from the light source to a liquid crystal display panel through alight guide plate and a plurality of optical sheets. The direct typebacklight has a plurality of light sources disposed directly under theliquid crystal display device, and the direct type backlight irradiateslight from the light sources to the liquid crystal display panel througha diffusion plate and a plurality of optical sheets.

Recently, the direct type backlight which has improved brightness, lightuniformity and color purity, versus the edge type backlight, is moreoften used in LCD TVs.

FIG. 1 is a diagram showing a liquid crystal display device of therelated art to which the direct type backlight is applied.

Referring to FIG. 1, the liquid crystal display device of the relatedart includes a liquid crystal display panel 11 and a backlight unit 10.Herein, the liquid crystal display panel 11 displays an image, and thebacklight unit 10 irradiates light to the liquid crystal display panel11.

A plurality of data lines and a plurality of gate lines (not shown inFIG. 1) are arranged to cross each other at the liquid crystal displaypanel 11. Liquid crystal cells are arranged in a matrix type between anupper substrate and a lower substrate. Furthermore, pixel electrodes andcommon electrodes (not shown), which apply an electric field to eachliquid crystal cell, are formed at the liquid crystal display panel 11.Thin film transistors (not shown) are formed at a crossing part of theplurality of data lines and the plurality of gate lines. Herein, thethin film transistors TFT switch a data voltage to be applied to a pixelelectrode in response to a scanning signal. Gate drive integratedcircuits and data drive integrated circuits are electrically connected,via a tape carrier package TCP (not shown), to the liquid crystaldisplay panel 11.

The backlight unit 10 includes a plurality of lamps 15, a bottom cover12, a diffusion plate 13, and a plurality of optical sheets 14.

The lamps 15 are radiated by an AC high voltage from an inverter (notshown) to supply a light to the diffusion plate 13.

The bottom cover 12 is manufactured in a container structure where theplurality of lamps 15 are received at an inner space, and a reflectionplate is formed at a bottom and a side surface of the inner space. Thediffusion plate 13 is assembled together with the bottom cover 12. Thediffusion plate 13 may include a plurality of beads, and disperseslight, using the beads, which is incident from a lamp. Accordingly, thediffusion plate 13 can minimize a brightness difference which isgenerated by a distance difference between the liquid crystal displaypanel and the lamp and a distance difference between the lamps. Sincethe diffusion plate 13 is such that the beads are spread into a mediumhaving the same refractive index, the diffusion plate 13 cannot condenselight.

The optical sheets 14 include at least one diffusion sheet and at leastone prism sheet to uniformly irradiate light incident from the diffusionplate 13 to an entire liquid crystal display panel 11. Furthermore, theoptical sheets 14 diffract a light progressing path toward a verticaldirection regarding a display surface of liquid crystal display panel 11to condense a light to a front surface of display surface of the liquidcrystal display panel 11.

The lamp 15 may largely be classified into a cold cathode fluorescentlamp (hereinafter, referred to as “CCFL”), an external electrodefluorescent lamp (hereinafter, referred to as “EEFL”), and a lightemitting diode (hereinafter, referred to as “LED”).

The liquid crystal display device of the related art keeps a distancebetween the liquid crystal display panel 11 and the lamps 15 in order toreduce a brightness difference between the lamps 15 to widen a diffusionspace of light which is generated from the lamps 15, and installs aplurality of lamps 15 to narrow a distance between the lamps 15.Accordingly, the liquid crystal display device of the related art has adisadvantage in that a thickness increases and manufacturing cost isincreased. Furthermore, in the liquid crystal display device of therelated art, since there is a limit to maintaining a distance betweenthe liquid crystal display panel 11 and the lamps 15 and increase in thenumber of the lamps 15, there is a limit to generating a uniformbrightness.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide aliquid crystal display device that may reduce manufacturing cost,contribute to a thin profile, and generate a uniform brightness, and afabricating method thereof.

In order to achieve these and other advantages of the invention, aliquid crystal display device according to the present inventioncomprises a liquid crystal display panel; and a backlight including aplurality of lamps, a diffusion plate which is located on the lamps, andan intermediate diffusion medium located between the lamps and thediffusion plate to diffuse light from the lamps, and irradiating a lightto the liquid crystal display panel.

The intermediate diffusion medium may include an external band of squaretype formed of a diffusion medium; and a plurality of ribs formed of thediffusion medium and connected to both sides of the external band ofsquare type, respectively.

Each of the ribs may be directly located over each of the lamps.

The ribs may include a plurality of first ribs which are directlylocated over the lamps; and a plurality of second ribs which are locatedbetween the first ribs.

The ribs may include a third rib which connects each of the ribs to eachother at an inner space of the external band of square type.

The liquid crystal display device according to the present invention mayfurther include a bottom cover receiving the lamps to an internal spaceand having an aperture part which is covered by the diffusion plate.

The liquid crystal display device according to the present invention mayfurther include a plurality of support members installed at the bottomcover to support at least one of the ribs or the external band of squaretype.

The liquid crystal display device according to the present invention mayfurther include a plurality of support members installed at the bottomcover to support at least one of the ribs or the external band of squaretype, and the lamps.

Another both sides of the external band of square type are directlylocated over the lamps.

The lamps may be any one of a cold cathode fluorescent lamp and anexternal electrode fluorescent lamp.

A liquid crystal display device according to the present inventioncomprises a liquid crystal display panel; and a backlight unit supplyinglight to the liquid crystal display panel, and the backlight unitincludes a plurality of direct type light sources; a diffusion platediffusing light which is emitted from the direct type light sourcestoward the liquid crystal display panel; and an intermediate diffusionmedium located between the diffusion plate and the direct type lightsources, and including a diffusion area overlapped with the direct typelight sources and a transmission area not overlapping with the lightsources.

A light which is emitted from the direct type light sources may beprimarily dispersed by the intermediate diffusion medium, and may besecondarily dispersed by the diffusion plate.

A method of fabricating a liquid crystal display device according to thepresent invention comprises molding a diffusion material using a mold toform an intermediate diffusion medium that includes a plurality of ribsconnected to an external band of square type and both sides of theexternal band of square type, respectively; and locating theintermediate diffusion medium between lamps and a diffusion plate.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages of the invention will be apparent from thefollowing detailed description of the embodiments of the presentinvention with reference to the accompanying drawings, in which:

In the Figures:

FIG. 1 is a diagram showing a liquid crystal display device of therelated art;

FIG. 2 is a diagram showing a liquid crystal display device according toan embodiment of the present invention;

FIG. 3 is a plan view showing the intermediate diffusion medium in FIG.2;

FIG. 4 is a sectional view showing an intermediate diffusion mediumaccording to another embodiment of the present invention;

FIG. 5 is a plan view showing the intermediate diffusion medium in FIG.4;

FIG. 6 is a diagram showing a support member which supports theintermediate diffusion medium according to the present invention; and

FIG. 7 is a diagram showing another example of the support member.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to FIGS. 2 to FIG. 7.

FIG. 2 is a diagram showing a liquid crystal display device according toan embodiment of the present invention.

Referring to FIG. 2, the liquid crystal display device according to thepresent invention includes a liquid crystal display panel 61 and abacklight unit 60. Herein, the backlight unit 60 irradiates light to theliquid crystal display panel 61.

Liquid crystal cells are arranged in an active matrix type between anupper substrate and a lower substrate to form the liquid crystal displaypanel 61. A plurality of data lines and a plurality of gate lines arearranged to cross each other on the lower substrate. A thin filmtransistor TFT is formed at each crossing part of the plurality of datalines and the plurality of gate lines. The TFT supplies a data signalfrom the data line to the liquid crystal cell in response to a scanningpulse from the gate line. A gate electrode of the TFT is connected tothe gate line, a source electrode of the TFT is connected to the dataline. Further, a drain electrode of the TFT is connected to a pixelelectrode of the liquid crystal cell. A storage capacitor, whichmaintains a voltage of the liquid crystal cell, is formed on a lowersubstrate of the liquid crystal display panel 61. The storage capacitormay be formed between the liquid crystal cell and the pre-stage gateline, and may be formed between the liquid crystal cell and a separatecommon line. A color filter, a common electrode, and a black matrix, forexample, are formed on an upper substrate of the liquid crystal displaypanel 61, and a polarizing plate which filters a linear polarization isformed at the upper substrate and the lower substrate. Furthermore, analignment film which sets a pre-tilt angle of liquid crystal moleculesis formed at the upper substrate and the lower substrate. The liquidcrystal molecules are driven by an electric field between a commonelectrode of the upper substrate and a pixel electrode of the lowersubstrate to modulate light incident from a backlight unit via apolarizing plate.

The backlight unit 60 includes a plurality of lamps 65, a bottom cover62, a diffusion plate 63, a plurality of optical sheets 64, and anintermediate diffusion medium 66.

The bottom cover 62 is manufactured in a container structure where theplurality of lamps 65 are located at an inner space, and a reflectionplate 67 is formed at a bottom and a side surface of the inner space.

The lamps 65 are radiated by an AC high voltage from an inverter (notshown) to generate light toward the diffusion plate 63.

The intermediate diffusion medium 66 is located on the lamps 65.

The intermediate diffusion medium 66 is located between the diffusionplate 63 and the lamps 65, and includes a diffusion area overlapped withthe lamps 65 and a transmission area not overlapping with the lamps 65.Such an intermediate diffusion medium 66 includes a diffusion mediumhaving a plurality of beads and primarily disperses light incident viathe lamps 65 using the beads.

The intermediate diffusion medium 66 will be described in detail withreference to FIG. 3. The intermediate diffusion medium 66 is formed tohave a plurality of first ribs 66 a and a second rib 66 b by molding adiffusion material using a mold. Herein, the plurality of first ribs 66a is connected to an external band of square type 66 c and both sides ofthe external band of square type 66 c, respectively. The second rib 66 bconnects the first ribs 66 a to each other. Another second rib 66 b′also connects the first ribs 66 a to each other, and an open area 66 dis formed between the second ribs 66 b and 66 b′. As illustrated in FIG.3, the length L₁ of the open area is more than the length L₂ of thesecond rib. A diffusion plate of the related art is manufactured by anextrusion method. However, since the intermediate diffusion medium 66according to the present invention has a plurality of ribs, theintermediate diffusion medium 66 according to the present inventioncannot be manufactured by the extrusion method. As a result, theintermediate diffusion medium 66 is manufactured by a molding method.

The first rib 66 a is directly located over the lamps 65 to transmit anddiffuse light which is generated from the lamps 65, and to reflect lightnot transmitted to the reflection plate 67. The second rib 66 b connectsthe first ribs 66 a to each other in order to prevent the first rib 66 afrom being transformed by its own weight and heat, and is formed to havea narrow width in order to minimize a brightness stain.

Another both sides among the external band of square type 66 c of theintermediate diffusion medium 66 are directly located over the lamps 65similar to the first rib 66 a, and carry out the same function as thefirst rib 66 a.

The diffusion plate 63 shields an aperture part of the bottom cover 62,and may be formed of the same material as the intermediate diffusionmedium 66. The diffusion plate 63 secondarily disperses light which isgenerated from the lamps 65 to be primarily dispersed via theintermediate diffusion medium 66 and light which is reflected to theintermediate diffusion medium 66 to be incident via the reflection plate67. In other words, the diffusion plate 63 can minimize a brightnessdifference which is generated by a distance difference between theliquid crystal display panel 61 and the lamp 65 and a distancedifference between the lamps 65. In this case, since the diffusion plate63 is manufactured in a structure where the beads are spread into amedium having the same refractive index, the diffusion plate 63 cannotcondense light.

The optical sheets 64 include at least one diffusion sheet and at leastone prism sheet to uniformly irradiate a light incident from thediffusion plate 63 to an entire liquid crystal display panel 61.Furthermore, the optical sheets 64 diffract a light progressing pathtoward a vertical direction regarding a display surface of the liquidcrystal display panel 61 to condense light to a front surface of displaysurface of the liquid crystal display panel 61.

A direct type lamp such as a cold cathode fluorescent lamp CCFL and anexternal electrode fluorescent lamp EEFL, for example, may be used asthe lamp 65.

As described above, the liquid crystal display device according to thepresent invention locates the intermediate diffusion medium 66 betweenthe lamp 65 and the diffusion plate 63 to increase diffusion of light.Thus, it is not necessary to widen a diffusion space of the lamp 65, sothat it becomes possible to make a thin profile of the liquid crystaldisplay device. Furthermore, the liquid crystal display device reducesthe number of lamp 65 to decrease manufacturing cost, have an excellentradiating effect, and decrease power consumption.

FIG. 4 and FIG. 5 are a sectional view and a plan view showing anintermediate diffusion medium according to another embodiment of thepresent invention.

Referring to FIG. 4 and FIG. 5, an intermediate diffusion medium 76according to another embodiment of the present invention is formed tohave a plurality of first ribs 76 a, a second rib 76 b, and a third rib76 c by molding a diffusion medium using a mold. Herein, the pluralityof first ribs 76 a is connected to an external band of square type 76 dand both sides of the external band of square type 76 d, respectively.The second rib 76 b is located in parallel to the first ribs 76 abetween the first ribs 76 a. The third rib 76 c connects the first ribs76 a to the second ribs 76 b.

The first rib 76 a is directly located over the lamps 65 to transmit anddiffuse light which is generated from the lamps 65, and to reflect lightwhich is transmitted to the reflection plate. The second rib 76 b isdirectly located between the first ribs 76 a, that is, is directlylocated over between the lamps 65 to diffuse light from the lamps 65 andre-diffuses light which is not transmitted to the first rib 76 a and arereflected to a reflection plate. The third rib 76 c connects the firstribs 76 a to the second ribs 76 b in order to prevent the first rib 76 aand the second ribs 76 b from being transformed by its own weight and aheat, and is formed to have a narrow width in order to minimize abrightness stain.

Another both sides among the external band of square type 76 d of theintermediate diffusion medium 76 are directly located over the lamps 65similar to the first rib 76 a, and carry out the same function as thefirst rib 76 a.

Only one second rib 76 b of the intermediate diffusion medium in FIG. 4and FIG. 5 is formed between the first ribs 76 a. However, at least onesecond rib 76 b may be formed between the first ribs 76 a.

FIG. 6 is a diagram showing a support member which supports theintermediate diffusion medium according to the present invention.

Referring to FIG. 6, the support member 68 includes a holder part 68 a,a support part 68 b, and a connecting part 68 c.

The holder part 68 a is formed to envelop an external band of squaretype of the intermediate diffusion mediums 66 and 76 or a rib, and hasan aperture part to be inserted the external band of square type of theintermediate diffusion mediums 66 and 76 or the rib. The support part 68b is located between the holder part 68 a and the connecting part 687 cto support the holder part 68 a. The connecting part 68 c is formed in asubstantially clamp shape in order to join the support member 68 withthe bottom cover 62. The bottom cover 62 and the reflection plate 67have a hole 69 to which the connecting part 68 c is inserted.

FIG. 7 is a diagram showing another example of the support member whichsupports the intermediate diffusion medium according to the presentinvention.

Referring to FIG. 7, the support member 78 includes a first holder part78 a, a second holder part 78 b, a support part 78 c, and a connectingpart 78 d. The first holder part 78 a is formed to envelop an externalband of square type of the intermediate diffusion mediums 66 and 76 or arib, and has an aperture part to be inserted the external band of squaretype of the intermediate diffusion mediums 66 and 76 or the rib. Thesecond holder part 78 b is formed to envelop a round part of the lamp65. In other words, the support member 68 in FIG. 6 plays a role tosupport only intermediate diffusion mediums 66 and 76. However, thesupport member 78 in FIG. 7 plays a role to support the intermediatediffusion mediums 66 and 76 together with the lamp 65. The support part78 c is formed to support the first holder part 78 a and the secondholder part 78 b in order that the support member 68 is supported withthe bottom cover 62 provided with the reflection plate 67. Theconnecting part 78 d is formed in a substantially clamp shape in orderto join the support member 68 with the bottom cover 62. The bottom cover62 and the reflection plate 67 have a hole 79 to which the connectingpart 78 d is inserted.

As described above, the liquid crystal display device and thefabricating method thereof according to the present invention locate theintermediate diffusion medium between the lamp and the diffusion plateto increase diffusion of light. Thus, it is not necessary to widen adiffusion space of the lamp, so that it becomes possible to make a thinprofile of the liquid crystal display device. Furthermore, the liquidcrystal display device according to the present invention reduces thenumber of lamps to decrease the manufacturing cost, have an excellentradiating effect, and decrease power consumption.

Although the present invention has been explained by the embodimentsshown in the drawings described above, it should be understood by thoseof ordinary skill in the art that the invention is not limited to theembodiments, but rather that various changes or modifications thereofare possible without departing from the spirit or scope of theinvention. Accordingly, the scope of the invention shall be determinedby the appended claims and their equivalents.

1. A liquid crystal display device, comprising: a liquid crystal displaypanel; and a backlight including a plurality of lamps, a diffusion platewhich is located on the lamps, and an intermediate diffusion mediumlocated between the lamps and the diffusion plate to diffuse light fromthe lamps, and irradiating light to the liquid crystal display panel,wherein the intermediate diffusion medium includes a first ribscorresponding with a diffusion area overlapped with the lamps and asecond ribs corresponding with a transmission area not overlapping withthe lamps, wherein the first ribs and the second ribs are connected toan external band of square type that is formed along the circumferenceof the edges of the first and second ribs, wherein the transmission areaincludes an open area and a second ribs, and wherein the length of theopen area is more than the length of the second rib.
 2. The liquidcrystal display device according to claim 1, further includes: a bottomcover receiving the lamps to an internal space and having an aperturepart which is covered by the diffusion plate.